Fourier transform infrared spectrophotometers (hereinafter abbreviated as “FTIR”) may be combined with an infrared microscope for performing micro-spectrophotometry in the infrared wavelength region. In such cases, a connection optical system is arranged between the FTIR and the infrared microscope main body, and the angle of the plane mirrors of the connection optical system is adjusted to properly align the optical axis of the infrared light beam from the FTIR and the optical axis of the infrared light introduction unit (optical system) of the infrared microscope main body.
The infrared microscope to which an infrared light beam has been supplied from the FTIR via the connection optical system irradiates that infrared light beam onto a specific small area (for example, a 15 μm×15 μm analysis position) on the surface of a sample. Based on functional groups of organic substances or the like, a spectrum specific to a molecular structure, etc. is generated from the specific small area on the sample surface, so identification and quantitation of organic substances and the like are performed by detecting and analyzing this spectrum (for example, see patent document 1).
Furthermore, the infrared microscope comprises an image acquisition unit such as a CCD camera or CMOS camera for observation of the sample surface by an analyst, and determination of analysis position on the sample surface and the like is performed while observing a visible light image of the sample surface using this image acquisition unit. For example, visible light from a light source such as a halogen lamp is irradiated onto a region including the analysis position on the sample surface, and visible light reflected by the region including the analysis position on the sample surface is detected with a CMOS camera, as a result of which, a visible light image based on the detected visible light is displayed. Based on this, the analyst designates the infrared light beam irradiation position on the sample or designates the analysis range on the sample while looking at the visible light image.
FIG. 4 is a drawing illustrating the main components of a conventional infrared microscope system. Here, one direction parallel to the ground is defined as the X direction, the direction parallel to the ground and perpendicular to the X direction is defined as the Y direction, and the direction perpendicular to the X direction and Y direction is defined as the Z direction.
The infrared microscope system comprises an infrared microscope 2 having an infrared microscope main body 200 and a connection optical system 80; an FTIR 20; and a computer 190 which performs control of the whole infrared microscope system.
The infrared microscope main body 200 comprises a sample stage 10 on which a sample S is placed; a visible light source unit 130 which outputs visible light; an image acquisition device 140 having a detection surface which detects visible light; a detection unit 50 which detects infrared light; cassegrain mirrors 60, 61; a transmission/reflection switching mirror 62; parabolic mirrors 63, 64; and a beam splitter 70.
While illustration of the details of the sample stage 10 has been omitted, it comprises a sample platform which is a mobile member, an X direction drive mechanism, a Y direction drive mechanism, and a Z direction drive mechanism.
A sample S can be placed onto and removed from the top surface of the sample platform. Such a sample platform can be moved in the desired X direction, Y direction and Z direction based on the necessary drive signals being outputted to the drive mechanisms by the computer 190.
The visible light source unit 130 is a halogen lamp which outputs illumination light including visible and near-infrared light of 400 nm to 1000 nm. The visible light source unit 130 is configured such that, after the optical path has been selected and switched between transmission measurement and reflection measurement by the transmission/reflection switching mirror 62, the outputted illumination light is converged by means of cassegrain mirror 60 (during reflection measurement) or cassegrain mirror 61 (during transmission measurement), and parabolic mirror 63 (during transmission measurement) or parabolic mirror 64 (during reflection measurement), and is irradiated onto a region including the analysis position on the surface of the sample S which has been placed onto the sample stage 10.
The image acquisition unit 140 comprises a CMOS camera 141 having a detection surface; and an infrared cut filter 142 and imaging lens 43 arranged in front of the CMOS camera 141. By means of this, illumination light including visible and near-infrared light of 400 nm to 1000 nm from the region including the analysis position on the surface of the sample S is converged by the cassegrain mirror 60 and advances in a predetermined direction (−Z direction), and visible light of 400 nm to 680 nm is then detected on the detection surface of the CMOS camera 141.
The detection unit 50 comprises an infrared detector (MCT) 51. By means of this, the infrared light beam from the analysis position on the sample S is converged by cassegrain mirror 60, 61, advances in a predetermined direction (−Z direction), and is reflected in the X direction by beam splitter 70 and is then detected by infrared detector 51.
The connection optical system 80 comprises a first plane mirror 81 for bending the infrared light beam from FTIR 20 by substantially 90°; a second plane mirror 82 for bending the infrared light beam from the first plane mirror 81 by substantially 90°; a screw adjustment mechanism (not illustrated) which adjusts the pitch angle of the first plane mirror 81; and a screw adjustment mechanism (not illustrated) which adjusts the yaw angle of the first plane mirror 81.
Here, the main components of FTIR 20 will be described using FIG. 5. FTIR 20 comprises a case 21 having a light beam extraction window (outlet) 21a, a Michelson interferometer 22, an infrared light source unit 23 which outputs an infrared light beam, a mobile mirror speed information detection unit 24, a detector 25, and a switching mirror 26 for switching the optical path to either the detector 25 or the light beam extraction window 21a. 
The Michelson interferometer 22 comprises a mobile mirror unit having a mobile mirror 22a, a stationary mirror unit having a stationary mirror 22b, and a beam splitter 22 arranged between the mobile mirror 22a and stationary mirror 22b. 
With a Michelson interferometer 22 of this sort, the infrared light beam outputted from the infrared light source unit 23 is irradiated onto the beam splitter 22c and is split by the beam splitter 22c into two directions, toward the mobile mirror 22a and stationary mirror 22b. The infrared light beam reflected by the mobile mirror 22a and the infrared light beam reflected by the stationary mirror 22b return to the beam splitter 22c and are combined and sent to the light beam extraction window 21a and detector 25. Here, the mobile mirror 22a moves forward and back in reciprocating fashion in the incident optical axis direction M, so the optical path length of the two split light beams changes periodically, and the light which heads from the beam splitter 22c toward the light beam extraction window 21a and detector 25 forms an interferogram whereof the amplitude fluctuates with time.
The infrared light source unit 23 comprises an infrared light source 23a which outputs an infrared light beam, a Jacquinot stop 23b capable of selecting and switching between circular apertures of different diameter, a parabolic mirror 23c, and a converging mirror 23d. By means of this, the infrared light beam outputted from the infrared light source 23a is irradiated via Jacquinot stop 23b and parabolic mirror 23c onto the beam splitter 22c of Michelson interferometer 22. It will be noted that the Jacquinot stop 23b has the function of determining the spectral resolution of FTIR 20, with the resolution increasing as the circular aperture is made smaller, enabling analysis of gaseous samples and the like requiring high spectral resolution.
Subsequently, the infrared light beam outputted from the light beam extraction window 21a passes through the connection optical system 80, and after the optical path has been selected and switched between transmission measurement and reflection measurement by the transmission/reflection switching mirror 62 of the infrared microscope main body 200, the infrared light beam is converged by cassegrain mirror 60 or cassegrain mirror 61 and parabolic mirror 63 or parabolic mirror 64 and is irradiated onto the analysis position (for example, 15 μm×15 μm) on the sample S which has been placed onto the sample stage 10.
Furthermore, the FTIR 20 is provided with a mobile mirror speed information detection unit 24 for detecting mobile mirror speed information. The mobile mirror speed information detection unit 24 performs speed information detection using a red laser light (632.8 nm), and comprises a He—Ne laser light source unit 24a which outputs red laser light, half-mirror 24b and half-mirror 24c which reflect red laser light, and laser light detector 24d (for example, see patent document 2).
With such a mobile mirror speed information detection unit 24, the red laser light outputted from the He—Ne laser light source unit 24a passes through half-mirror 24b and is irradiated onto beam splitter 22c, and is split in two directions toward mobile mirror 22a and stationary mirror 22b by the beam splitter 22c. The red laser light reflected by the mobile mirror 22a and the red laser light reflected by the stationary mirror 22b then return to the beam splitter 22c and are combined. Here as well, the mobile mirror 22a is similarly moving in reciprocating fashion back and forth in the incident optical axis direction M, so the difference in optical path length of the two split light beams changes periodically, and the light heading from the beam splitter 22c toward the laser light detector 24b constitutes laser interference light whereof the amplitude fluctuates with time. The position, movement speed, etc. of the mobile mirror 22a is computed on the basis of the detection signal of the laser light detector 24d, i.e., based on a laser light interference fringe signal. Here, the laser interference light is sent to the light beam extraction window 21a and detector 25 as return light from the beam splitter 22c. 
In an infrared microscope system of this sort, there is a need to perform an adjustment operation to properly align the optical axis of the infrared light beam from the FTIR 20 with the optical axis of the optical system of the infrared microscope main body 200.
Here, this adjustment operation will be described. First, the operator (analyst, etc.) installs the connection optical system 80 between FTIR 20 and infrared microscope main body 200. Next, the operator causes red laser light to be outputted from the He—Ne laser light source unit 24a of FTIR 20. Next, the operator performs rough adjustment of the angle of the first plane mirror 81 using as a guide the red laser light which has entered Michelson interferometer 22 from the He—Ne laser light source unit 24a and has returned from the beam splitter 22c. Here, graph paper or the like to serve as a laser target is placed over the second plane mirror 82 to which the red laser light is guided from the first plat mirror 81, and rough adjustment is performed using the screw adjustment mechanism while visually checking the position of the red laser light on the target. Next, the operator causes an infrared light beam to be outputted from the infrared light source unit 23 of FTIR 20. Next, while looking at the infrared spectrum based on the output signal from the infrared detector 51, the operator performs fine adjustment of the angle of the first plane mirror 81 using the screw adjustment mechanism such that infrared power is maximized (see FIG. 3).